U.S. patent application number 14/436034 was filed with the patent office on 2015-09-24 for motor control device and motor drive device.
The applicant listed for this patent is RENESAS ELECTRONIC CORPORATION. Invention is credited to Hisaaki Watanabe.
Application Number | 20150270796 14/436034 |
Document ID | / |
Family ID | 50544229 |
Filed Date | 2015-09-24 |
United States Patent
Application |
20150270796 |
Kind Code |
A1 |
Watanabe; Hisaaki |
September 24, 2015 |
MOTOR CONTROL DEVICE AND MOTOR DRIVE DEVICE
Abstract
A sampling period of information according to a load state of an
alternating-current motor is controlled so as to be variable with
respect to a carrier period of a PWM circuit, and a predetermined
arithmetic operation for aggregating information sampled in one
period of the carrier period is performed in a separate arithmetic
circuit from a CPU. Thereby, in a situation where the rotation of
the alternating-current motor becomes too fast with respect to the
carrier period, motor rotation control for suppressing a sudden
fluctuation of a motor load can be performed by faster reaction
while suppressing an increase in an arithmetic control load of a
CPU.
Inventors: |
Watanabe; Hisaaki;
(Kawasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RENESAS ELECTRONIC CORPORATION |
Kawasaki-shi, Kanagawa |
|
JP |
|
|
Family ID: |
50544229 |
Appl. No.: |
14/436034 |
Filed: |
October 26, 2012 |
PCT Filed: |
October 26, 2012 |
PCT NO: |
PCT/JP2012/077732 |
371 Date: |
April 15, 2015 |
Current U.S.
Class: |
318/400.05 |
Current CPC
Class: |
Y02T 10/643 20130101;
B60L 15/025 20130101; Y02T 10/7275 20130101; B60L 2240/12 20130101;
Y02T 10/7005 20130101; H02P 21/0003 20130101; B60L 2240/423
20130101; B60L 50/51 20190201; B60L 2240/465 20130101; B60L
2240/421 20130101; Y02T 10/70 20130101; Y02T 10/64 20130101; B60L
15/007 20130101; B60L 15/20 20130101; Y02T 10/72 20130101; B60L
3/106 20130101; B60L 2220/12 20130101; H02P 27/085 20130101; B60L
2240/461 20130101 |
International
Class: |
H02P 6/08 20060101
H02P006/08 |
Claims
1. A motor control device comprising: a PWM circuit for performing
switch control on an inverter that outputs a drive current to an
alternating-current motor through a PWM pulse signal; a CPU that
performs feedback control on a duty of the PWM pulse signal; and an
arithmetic unit, in which a sampling period of feedback information
is made variable, and which performs predetermined arithmetic
processing for aggregating the feedback information acquired in the
sampling period shorter than a carrier period of the PWM circuit in
a comparison target for one period of the carrier period in case
that a predetermined load fluctuation is generated in the
alternating-current motor, wherein the CPU controls the duty of the
PWM pulse signal after the predetermined load fluctuation is
generated, on the basis of an arithmetic result in the arithmetic
unit and a drive command value.
2. The motor control device according to claim 1, wherein the
feedback information is a motor current value which is obtained by
performing AD conversion on a current which is fed back from an
alternating-current motor and a rotor rotation angle value which is
obtained from a rotor position of the alternating-current
motor.
3. The motor control device according to claim 2, wherein in case
that a predetermined load fluctuation is generated in the
alternating-current motor, the control unit includes a control
circuit that controls a sampling period of feedback information so
as to be variable, and an arithmetic circuit that performs the
predetermined arithmetic processing, and the control circuit
determines whether a predetermined load fluctuation is generated in
the alternating-current motor, shortens a period in which the
feedback information is acquired until control of the
alternating-current motor follows the load fluctuation in case that
the load fluctuation is determined to be generated, and performs
control for returning the period in which the feedback information
is acquired to a reference value in case that the control of the
alternating-current motor follows the load fluctuation.
4. The motor control device according to claim 3, wherein the CPU
initializes the period in which the feedback information is
acquired, and the control circuit sets the initialized period to a
control target.
5. The motor control device according to claim 4, wherein the
control circuit senses the predetermined load fluctuation from the
rotor rotation angle value or the motor current value.
6. The motor control device according to claim 4, wherein the
control circuit further predicts the predetermined load fluctuation
from state detection information of a traveling surface that
receives a rotational force of the alternating-current motor.
7. The motor control device according to claim 3, wherein the
predetermined arithmetic processing in the arithmetic circuit
includes coordinate conversion processing for converting the motor
current value and the rotor rotation angle value into a two-phase
current value, and filter arithmetic processing or average
arithmetic processing for the two-phase current value on which
coordinate conversion is performed.
8. The motor control device according to claim 7, wherein the
control circuit further changes a gain of the filter arithmetic
processing or the average arithmetic processing in the arithmetic
circuit, as necessary, in case that the period in which the
feedback information is acquired is set to be short, and performs
control for returning the gain of the filter arithmetic processing
or the average arithmetic processing to the initial value in case
that the period in which the feedback information is acquired is
returned to the reference value.
9. The motor control device according to claim 8, wherein the CPU
initializes the gain of the filter arithmetic processing or the
average arithmetic processing, and the control circuit sets the
initialized gain to a control target.
10. The motor control device according to claim 7, wherein the
control circuit controls an AD conversion startup trigger interval
of AD conversion processing of the fed-back current and a fetching
interval of the rotor rotation angle value to the arithmetic
circuit, to thereby determine the period in which the feedback
information is acquired.
11. The motor control device according to claim 2, wherein the
control unit includes the arithmetic circuit that performs the
predetermined arithmetic processing, and the CPU controls a
sampling period of feedback information so as to be variable,
determines whether a predetermined load fluctuation is generated in
the alternating-current motor, shortens a period in which the
feedback information is acquired until control of the
alternating-current motor follows the load fluctuation in case that
the load fluctuation is determined to be generated, and returns the
period in which the feedback information is acquired to a reference
value in case that the control of the alternating-current motor
follows the load fluctuation.
12. The motor control device according to claim 11, wherein the CPU
senses the predetermined load fluctuation from the rotor rotation
angle value or the motor current value.
13. The motor control device according to claim 12, wherein the CPU
further predicts the predetermined load fluctuation from state
detection information of a traveling surface that receives a
rotational force of the alternating-current motor.
14. The motor control device according to claim 11, wherein the
predetermined arithmetic processing in the arithmetic circuit
includes coordinate conversion processing for converting the motor
current value and the rotor rotation angle value into a two-phase
current value, and filter arithmetic processing or average
arithmetic processing for the two-phase current value on which
coordinate conversion is performed.
15. The motor control device according to claim 14, wherein the CPU
changes a gain of the filter arithmetic processing or the average
arithmetic processing in the arithmetic circuit, as necessary, in
case that the period in which the feedback information is acquired
is set to be short, and performs control for returning the gain of
the filter arithmetic processing or the average arithmetic
processing to the initial value in case that the period in which
the feedback information is acquired is returned to the reference
value.
16. The motor control device according to claim 14, wherein the CPU
controls an AD conversion startup trigger interval of AD conversion
processing of the fed-back current and a fetching interval of the
rotor rotation angle value to the arithmetic circuit, to thereby
determine the acquisition period of the feedback information.
17. The motor control device according to claim 1, wherein the
motor control device is constituted by a microcomputer which is
formed as a semiconductor integrated circuit in a silicon
substrate.
18. A motor drive device that drives an alternating-current motor
for vehicle traveling, comprising: an inverter that supplies a
motor current to the alternating-current motor; and a motor control
device that performs feedback control on a motor current which is
output by the inverter on the basis of a drive command value,
wherein the motor control device includes a PWM circuit that
performs switch control on the inverter through a PWM pulse signal,
a CPU that performs feedback control on a duty of the PWM pulse
signal, and an arithmetic unit, in which a sampling period of
feedback information is made variable, and which performs
predetermined arithmetic processing for aggregating a plurality of
pieces of the feedback information acquired in the sampling period
shorter than a carrier period of the PWM circuit in a comparison
target for one period of the carrier period in case that a
predetermined load fluctuation is generated in the
alternating-current motor, and the CPU controls the duty of the PWM
pulse signal after the predetermined load fluctuation is generated,
on the basis of an arithmetic result in the arithmetic unit and the
drive command value.
19. The motor drive device according to claim 18, wherein the
feedback information is a motor current value which is obtained by
performing AD conversion on a current which is fed back from the
alternating-current motor and a rotor rotation angle value which is
obtained from a rotor position of the alternating-current
motor.
20. The motor drive device according to claim 19, wherein the
control unit includes a control circuit that controls a sampling
period of feedback information so as to be variable in case that a
predetermined load fluctuation is generated in the
alternating-current motor, and an arithmetic circuit that performs
the predetermined arithmetic processing, and the control circuit
determines whether a predetermined load fluctuation is generated in
the alternating-current motor, shortens a period in which the
feedback information is acquired until control of the
alternating-current motor follows the load fluctuation in case that
the load fluctuation is determined to be generated, and performs
control for returning the period in which the feedback information
is acquired to a reference value in case that the control of the
alternating-current motor follows the load fluctuation.
Description
TECHNICAL FIELD
[0001] The invention relates to a motor control that performs PWM
(Pulse-width modulation) control on the supply of a motor current
to an alternating-current motor in accordance with a drive command
and feedback information, particularly, a sampling technique of
feedback information for a carrier period of PWM, and relates to a
technique effective in a case of application to PWM motor control
of, for example, an electric vehicle (EV) or a hybrid vehicle
(HV).
BACKGROUND ART
[0002] In PWM control for an alternating-current motor of an EV or
an HV, a current command value generated on the basis of a motor
control logic such as vector control which is mounted in a control
circuit is given to a PWM circuit, to thereby generate a PWM pulse
for applying an output voltage having any amplitude and phase from
an inverter to an alternating-current motor. Control of a torque
which is generated by the interaction of a motor current with a
magnetic flux which is interlinked with a winding of the
alternating-current motor is required for controlling the
rotational speed of an alternating-current motor and the position
of a rotor at high speed. For this reason, the control circuit
generates a current command value to a drive command for each phase
while referring to current information which is fed back from a
feedback loop of the motor current or position information of the
rotor, and gives the generated value to the PWM circuit. Such
general PWM control for the alternating-current motor is disclosed
in, for example, PTL 1.
[0003] In the PWM control for the alternating-current motor, the
rotation speed of the alternating-current motor is sufficiently
slow in a carrier period of the PWM circuit. Thus, in case that a
motor current acquisition period corresponding to the carrier
period is generated in the acquisition of the motor current from
the feedback loop, it is possible to acquire a sinusoidal motor
current, and to reflect arithmetic results based on the fed-back
motor current or the like in the PWM pulse. For example, in case
that a sinusoidal wave is represented by more than twelve divisions
with respect to a carrier period having a frequency of 10 kHz, the
rotation speed of the alternating-current motor can attain up to
833 Hz.
CITATION LIST
Patent Literature
[0004] PTL 1: Domestic Re-publication of PCT Patent Application No.
2010/109964
DISCLOSURE OF THE INVENTION
Problems that the Invention is to Solve
[0005] The inventor has examined a case where the rotation speed of
an alternating-current motor becomes too fast with respect to a
carrier period of a PWM circuit. In case that the rotation of the
alternating-current motor becomes too fast with respect to the
carrier period, a motor current is not able to be acquired in a
sinusoidal shape. In this case, the shortening of a current
acquisition period makes it possible to acquire a current, but a
PWM pulse to be reflected is dependent on the carrier period, and
thus feedback current values acquired during the carrier period
have to be arithmetically calculated collectively by filtering or
averaging, to thereby reflect the resultant in a duty of the PWM
pulse. In this case, arithmetic responsiveness of filtering or
averaging is dependent on a current acquisition period or a filter
gain, and thus controllability deteriorates as compared to normal
control. In addition, in a high-rotation region of the
alternating-current motor, since a load of arithmetic control of a
CPU has a tendency to become larger to make matters worse, the
shortening of a sampling interval of a feedback current causes a
further increase in the load of the CPU. Thus, it was made clear
that there might be a concern of the sampling interval of the
feedback current not being able to be sufficiently shortened.
Particularly, a situation where the rotation speed of the
alternating-current motor which is a traveling drive source of an
EV or an HV becomes too fast with respect to the carrier period is
assumed to be generated by the skidding of a wheel due to a slip.
This may be an induction factor for an accident caused by sudden
acceleration, abrupt steering, road surface freezing, and the like.
Thus, a sudden fluctuation of the load has to be suppressed by at
least faster reaction to the skidding of a wheel. Therefore, it is
necessary to control the rotational speed of a motor in a direction
in which a sudden fluctuation of a load is suppressed by faster
reaction to a situation where the rotation of the
alternating-current motor becomes too fast with respect to the
carrier period.
[0006] The foregoing and other problems and novel features for
solving the problems will be made clearer from the description of
the present specification and the accompanying drawings.
Means for Solving the Problems
[0007] The following is a brief description of the representative
embodiments disclosed in the present application.
[0008] That is, a sampling period of information according to a
load state of an alternating-current motor is controlled so as to
be variable with respect to a carrier period of a PWM circuit, and
a predetermined arithmetic operation for aggregating information
sampled in one period of the carrier period is performed in a
separate arithmetic circuit from a CPU.
Effects of the Invention
[0009] The following is a brief description of an effect obtained
by the representative embodiments of the invention disclosed in the
present application.
[0010] That is, in a situation where the rotation of the
alternating-current motor becomes too fast with respect to the
carrier period, motor rotation control for suppressing a sudden
fluctuation of a motor load can be performed by faster reaction
while suppressing an increase in an arithmetic control load of a
CPU.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a block diagram illustrating an example of a motor
drive device.
[0012] FIG. 2 is a block diagram illustrating, in principle, a PWM
control function for vector control of an alternating-current motor
in a CPU and an arithmetic function of an accelerator.
[0013] FIG. 3 is a diagram conceptually illustrating a case where a
sampling period in which motor current values iv and iw and an
electrical angle .theta. are acquired and a carrier period are
coincident with each other.
[0014] FIG. 4 is a diagram illustrating a case where a motor drive
current is not easily represented by a sinusoidal wave through a
PWM pulse in a motor current having a high frequency due to a fast
motor rotation.
[0015] FIG. 5 is a diagram conceptually illustrating a process in
case that the sampling period in which the motor current values iv
and iw and the electrical angle .theta. are acquired is made
shorter than the carrier period.
[0016] FIG. 6 is a block diagram illustrating a configuration of an
accelerator for performing synchronous control of the sampling
period.
[0017] FIG. 7 is a flow diagram illustrating a processing procedure
of autonomous synchronous control of the sampling period together
with a synchronous control procedure of the sampling period in a
CPU.
[0018] FIG. 8 is a diagram illustrating a processing mode for
shortening the sampling period halfway in case that a great load
fluctuation is detected in the middle of the carrier period in the
autonomous synchronous control of the sampling period.
[0019] FIG. 9 is a diagram illustrating a control mode in the
skidding of a wheel and the return thereof to a normal
rotation.
[0020] FIG. 10 is a diagram illustrating an operation mode in case
that the carrier period is changed together with the sampling
period with respect to the sudden fluctuation of a load.
[0021] FIG. 11 is a diagram illustrating a processing mode in which
the number of times of sampling with the carrier period is made
variable in accordance with a motor load (motor rotation speed) in
the synchronous control of the sampling period in a CPU.
[0022] FIG. 12 is a block diagram illustrating a configuration of
the accelerator in which a CPU is burdened with a control function
of a control circuit in the accelerator of FIG. 6.
BEST MODE FOR CARRYING OUT THE INVENTION
1. Summary of the Embodiments
[0023] First, summary of representative embodiments of the
invention disclosed in the application will be described. Reference
numerals in drawings in parentheses referred to in description of
the summary of the representative embodiments just denote
components included in the concept of the components to which the
reference numerals are designated.
[0024] [1] <Making Sampling Period of Load Fluctuation Variable
with Respect to PWM Carrier Period>
[0025] A motor control device (13) according to a representative
embodiment includes a PWM circuit (23) for performing switch
control on an inverter (10) that outputs a drive current to an
alternating-current motor (2) through a PWM pulse signal (Pu, Pv,
Pw), a CPU (20) that performs feedback control on a duty of the PWM
pulse signal, and an arithmetic unit (26, 26A), in which a sampling
period of feedback information (iv, iw, .theta.) is made variable,
and which performs predetermined arithmetic processing for
aggregating the feedback information acquired in the sampling
period shorter than a carrier period of the PWM circuit in a
comparison target for one period of the carrier period in case that
a predetermined load fluctuation is generated in the
alternating-current motor. The CPU controls the duty of the PWM
pulse signal after the predetermined load fluctuation is generated,
on the basis of an arithmetic result in the arithmetic unit and the
drive command value.
[0026] According to this, it is possible to acquire the feedback
information in a period shorter than the carrier period in
accordance with a predetermined fluctuation of a motor load, and to
burden the arithmetic unit with an arithmetic operation for
aggregating a plurality of pieces of feedback information, acquired
in the carrier period alone, in the comparison target for one
period of the carrier period. Therefore, in a situation where the
rotation of the alternating-current motor becomes too fast with
respect to the carrier period, motor rotation control for
suppressing a sudden fluctuation of a motor load can be performed
by faster reaction while suppressing an increase in an arithmetic
control load of a CPU.
[0027] [2] <Information of Motor Current and Rotor Angle of
Motor>
[0028] In item 1, the feedback information is a motor current value
(iv, iw) which is obtained by performing AD conversion on a current
which is fed back from an alternating-current motor and a rotor
rotation angle value (.theta.) which is obtained from a rotor
position of the alternating-current motor.
[0029] According to this, the motor control device is suitable for
vector control of the alternating-current motor.
[0030] [3] <Control Circuit Detects Load Fluctuation to Change
Sampling Period>
[0031] In item 2, in case that a predetermined load fluctuation is
generated in the alternating-current motor, the control unit (26)
includes a control circuit (46) that controls a sampling period of
feedback information so as to be variable, and an arithmetic
circuit (47) that performs the predetermined arithmetic processing.
The control circuit determines whether a predetermined load
fluctuation is generated in the alternating-current motor, shortens
a period in which the feedback information is acquired until
control of the alternating-current motor follows the load
fluctuation in case that the load fluctuation is determined to be
generated, and performs control for sequentially returning the
period in which the feedback information is acquired to a reference
value in case that the control of the alternating-current motor
follows the load fluctuation.
[0032] According to this, it is possible to burden the control
circuit with control of the acquisition period of the feedback
information until the alternating-current motor skids due to a slip
or the like and then recovers. It is possible to reduce a burden of
the CPU in this point.
[0033] [4] <CPU Initializes Acquisition Period of Feedback
Information>
[0034] In item 3, the CPU initializes the period in which the
feedback information is acquired, and the control circuit sets the
initialized period to a control target.
[0035] According to this, separately from the control of the
acquisition period of the feedback information in the control
circuit, the CPU requires setting control of the carrier period of
the PWM circuit in accordance with a relationship with a rotation
torque required for the feedback control, and thus it is
economical, in view of a system, for the CPU to initialize a period
in which the feedback information is acquired in the relationship
with the rotation torque.
[0036] [5] <Load Fluctuation Sensing in Control Circuit (Rotor
Angle, Motor Current)>
[0037] In item 3, the control circuit senses the predetermined load
fluctuation from the rotor rotation angle value or the motor
current value.
[0038] According to this, it is possible to easily acquire the
fluctuation of the motor load without imposing a burden on the
CPU.
[0039] [6] <Load Fluctuation Sensing in Control Circuit (State
Detection Information of Traveling Surface)>
[0040] In item 5, the control circuit further predicts the
predetermined load fluctuation from state detection information
(RDST) of a traveling surface that receives a rotational force of
the alternating-current motor.
[0041] According to this, the fluctuation of the motor load is
predicted, and thus motor rotation control for suppressing a sudden
fluctuation of the motor load can be performed by faster
reaction.
[0042] [7] <Filter Arithmetic Operation, Averaging Arithmetic
Operation>
[0043] In item 3, the predetermined arithmetic processing in the
arithmetic circuit includes coordinate conversion processing
(coordinate conversion portion 40) for converting the motor current
value and the rotor rotation angle value into a two-phase current
value, and filter arithmetic processing or average arithmetic
processing (aggregate arithmetic portions 41d and 41q) for the
two-phase current value on which coordinate conversion is
performed.
[0044] According to this, the motor control device is suitable for
a case where the alternating-current motor is driven using
coordinate conversion by a direct-current power supply, and it is
possible to easily aggregate a plurality of pieces of information
by using the filter arithmetic processing or the average arithmetic
processing.
[0045] [8] <Arithmetic Gain Control in Control Circuit>
[0046] In item 7, the control circuit further changes a gain of the
filter arithmetic processing or the average arithmetic processing
in the arithmetic circuit, as necessary, in case that the period in
which the feedback information is acquired is set to be short, and
performs control for returning the gain of the filter arithmetic
processing or the average arithmetic processing to the initial
value in case that the period in which the feedback information is
acquired is returned to the reference value.
[0047] According to this, it is possible to decrease the gains in
accordance with an increase in the number of acquisitions of the
feedback information so that a response does not become sensitive
without imposing a burden on the CPU, or to keep the gains
unchanged due to a fast response in case that the number of
acquisitions of the feedback information increases.
[0048] [9] <Initialization of Gain in CPU>
[0049] In item 8, the CPU initializes the gain of the filter
arithmetic processing or the average arithmetic processing, and the
control circuit sets the initialized gain to a control target.
[0050] According to this, separately from the control of the
acquisition period of the feedback information in the control
circuit, the CPU also requires gain setting depending on the
setting of the carrier period of the PWM circuit in accordance with
a relationship with a rotation torque required for the feedback
control, and thus it is economical, in view of a system for the CPU
to initialize a gain of the filter arithmetic processing or the
average arithmetic processing in the relationship with the rotation
torque.
[0051] [10] <Sampling Period Control in Control Circuit; Startup
Trigger Interval of AD Conversion>
[0052] In item 7, the control circuit controls an AD conversion
startup trigger interval of AD conversion processing of the
fed-back current and a fetching interval of the rotor rotation
angle value to the arithmetic circuit, to thereby determine the
period in which the feedback information is acquired.
[0053] According to this, in follow-up control, it is possible to
easily control the sampling period of the feedback information for
obtaining the feedback information without imposing a burden on the
CPU.
[0054] [11] <CPU Detects Load Fluctuation to Change Sampling
Period>
[0055] In items 11 to 16, a function of the follow-up control
portion in items 3 to 10 is replaced by a CPU. In item 2, the
control unit (26A) includes an arithmetic circuit (47) that
performs the predetermined arithmetic processing, and the CPU
controls a sampling period of feedback information so as to be
variable, determines whether a predetermined load fluctuation is
generated in the alternating-current motor, shortens a period in
which the feedback information is acquired until control of the
alternating-current motor follows the load fluctuation in case that
the load fluctuation is determined to be generated, and returns the
acquisition period of the feedback information to a reference value
in case that the control of the alternating-current motor follows
the load fluctuation.
[0056] According to this, a burden of the CPU increases in the
control of the acquisition period of the feedback information as
compared to item 3, but it is possible to cope with the burden
flexibly through software of the CPU.
[0057] [12] <Load Fluctuation Sensing in CPU (Rotor Angle, Motor
Current)>
[0058] In item 11, the CPU senses the predetermined load
fluctuation from rotor location information of a motor or a motor
current.
[0059] According to this, a burden of the CPU increases as compared
to item 5, but it is possible to easily acquire the fluctuation of
the motor load.
[0060] [13] <Load Fluctuation Sensing in CPU (State Detection
Information of Traveling Surface)>
[0061] In item 12, the CPU further predicts the predetermined load
fluctuation from state detection information of a traveling surface
that receives a rotational force of the alternating-current
motor.
[0062] According to this, a burden of the CPU increases as compared
to item 6, but the fluctuation of the motor load is predicted, and
thus motor rotation control for suppressing a sudden fluctuation of
the motor load can be performed by faster reaction.
[0063] [14] <Filter Arithmetic Operation, Averaging Arithmetic
Operation>
[0064] In item 11, the predetermined arithmetic processing in the
arithmetic circuit includes coordinate conversion processing for
converting the motor current value and the rotor rotation angle
value into a two-phase current value, and filter arithmetic
processing or average arithmetic processing for the two-phase
current value on which coordinate conversion is performed.
[0065] According to this, the motor control device is suitable for
a case where the alternating-current motor is driven using
coordinate conversion by a direct-current power supply, and it is
possible to easily aggregate a plurality of pieces of information
by using the filter arithmetic processing or the average arithmetic
processing.
[0066] [15] <Arithmetic Gain Control in CPU>
[0067] In item 14, the CPU changes a gain of the filter arithmetic
processing or the average arithmetic processing in the arithmetic
circuit, as necessary, in case that the period in which the
feedback information is acquired is set to be short, and performs
control for returning the gain of the filter arithmetic processing
or the average arithmetic processing to the initial value in case
that the period in which the feedback information is acquired is
returned to the reference value.
[0068] According to this, a burden of the CPU increases as compared
to item 8, but, it is possible to decrease the gains in accordance
with an increase in the number of acquisitions of the feedback
information so that a response does not become sensitive without
imposing a burden on the CPU, or to keep the gains unchanged due to
a fast response in case that the number of acquisitions of the
feedback information increases.
[0069] [16] <Sampling Period in CPU; Startup Trigger Interval of
AD Conversion>
[0070] In item 14, the CPU controls an AD conversion startup
trigger interval of AD conversion processing of the fed-back
current and a fetching interval of the rotor rotation angle value
to the arithmetic circuit, to thereby determine the acquisition
period of the feedback information.
[0071] According to this, in the follow-up control, a burden of the
CPU increases as compared to item. 10, but it is possible to easily
control the sampling period of the feedback information for
obtaining the feedback information.
[0072] [17] <Microcomputer>
[0073] In any one of items 1 to 16, the motor control device is
constituted by a microcomputer which is formed as a semiconductor
integrated circuit in a silicon substrate.
[0074] According to this, it is possible to contribute to a
reduction in the size of the motor control device.
[0075] [18] <Making Sampling Period of Load Fluctuation Variable
with respect to PWM Carrier Period>
[0076] A motor drive device (1) according to another embodiment
different from that in items 1 to 18, the device driving an
alternating-current motor (2) for vehicle traveling, includes an
inverter (10) that supplies a motor current to the
alternating-current motor, a motor control device (13) that
performs feedback control on a motor current which is output by the
inverter on the basis of a drive command. The motor control device
includes a PWM circuit (23) that performs switch control on the
inverter through a PWM pulse signal (Pu, Pv, Pw), a CPU (20) that
performs feedback control on a duty of the PWM pulse signal, and an
arithmetic unit (26, 26A), in which a sampling period of feedback
information (id, iq, .theta.) is made variable, and which performs
predetermined arithmetic processing for aggregating a plurality of
pieces of the feedback information acquired in the sampling period
shorter than a carrier period of the PWM circuit in a comparison
target for one period of the carrier period in case that a
predetermined load fluctuation is generated in the
alternating-current motor. The CPU controls the duty of the PWM
pulse signal after the predetermined load fluctuation is generated,
on the basis of an arithmetic result in the arithmetic unit and the
drive command value.
[0077] According to this, it is possible to acquire the feedback
information in a period shorter than the carrier period in
accordance with a predetermined fluctuation of a motor load, and to
burden the arithmetic unit with an arithmetic operation for
aggregating a plurality of pieces of feedback information, acquired
in the carrier period alone, in the comparison target for one
period of the carrier period. Therefore, in a situation where the
rotation of the alternating-current motor becomes too fast with
respect to the carrier period, motor rotation control for
suppressing a sudden fluctuation of a motor load can be performed
by faster reaction while suppressing an increase in an arithmetic
control load of a CPU. Thus, it is possible to suppress a sudden
fluctuation of the load by at least faster reaction to the skidding
of a wheel, and to contribute to prevent an accident which is
generated by the skid of a wheel due to a slip caused by sudden
acceleration, abrupt steering, freezing road surface, and the like
in an EV, an HV or the like.
[0078] [19] <Information of Motor Current and Rotor Angle of
Motor>
[0079] In item 18, the feedback information is a motor current
value which is obtained by performing AD conversion on a current
which is fed back from the alternating-current motor and a rotor
rotation angle value which is obtained from a rotor position of the
alternating-current motor.
[0080] According to this, the same operational effect as that of
item 2 is exhibited.
[0081] [20] <Control Circuit Detects Load Fluctuation to Change
Sampling Period>
[0082] In item 19, the control unit (26) includes a control circuit
(46) that controls a sampling period of feedback information so as
to be variable in case that a predetermined load fluctuation is
generated in the alternating-current motor, and an arithmetic
circuit (47) that performs the predetermined arithmetic processing.
The control circuit determines whether a predetermined load
fluctuation is generated in the alternating-current motor, shortens
a period in which the feedback information is acquired until
control of the alternating-current motor follows the load
fluctuation in case that the load fluctuation is determined to be
generated, and performs control for sequentially returning the
period in which the feedback information is acquired to a reference
value in case that the control of the alternating-current motor
follows the load fluctuation.
[0083] According to this, the same operational effect as that of
item 2 is exhibited.
[0084] [21] <CPU Initializes Acquisition Period of Feedback
Information>
[0085] In item 20, the CPU initializes the period in which the
feedback information is acquired, and the follow-up control portion
sets the initialized period to a control target.
[0086] According to this, the same operational effect as that of
item 4 is exhibited.
[0087] [22] <Load Fluctuation Sensing in Control Circuit (Rotor
Angle, Motor Current)>
[0088] In item 20, the control circuit senses the predetermined
load fluctuation from the rotor rotation angle value or the motor
current value.
[0089] According to this, the same operational effect as that of
item 5 is exhibited.
[0090] [23] <Load Fluctuation Sensing in Control Circuit (State
Detection Information of Traveling Surface)>
[0091] In item 22, the control circuit further predicts the
predetermined load fluctuation from state detection information of
a traveling road surface of a vehicle.
[0092] According to this, the same operational effect as that of
item 6 is exhibited.
[0093] [24] <Filter Arithmetic Operation, Averaging Arithmetic
Operation>
[0094] In item 20, the predetermined arithmetic processing in the
arithmetic circuit includes coordinate conversion processing for
converting the motor current value and the rotor rotation angle
value into a two-phase current value, and filter arithmetic
processing or average arithmetic processing for the two-phase
current value on which coordinate conversion is performed.
[0095] According to this, the same operational effect as that of
item 7 is exhibited.
[0096] [25] <Arithmetic Gain Control in Control Circuit>
[0097] In item 24, the control circuit further changes a gain of
the filter arithmetic processing or the average arithmetic
processing in the arithmetic circuit, as necessary, in case that
the period in which the feedback information is acquired is set to
be short, and performs control for returning the gain of the filter
arithmetic processing or the average arithmetic processing to the
initial value in case that the period in which the feedback
information is acquired is returned to the reference value.
[0098] According to this, the same operational effect as that of
item 8 is exhibited.
[0099] [26] <Initialization of Gain in CPU>
[0100] In item 25, the CPU initializes the gain of the filter
arithmetic processing or the average arithmetic processing, and the
control circuit sets the initialized gain to a control target.
[0101] According to this, the same operational effect as that of
item 9 is exhibited.
[0102] [27] <Sampling Period Control in Control Circuit; Startup
Trigger Interval of AD Conversion>
[0103] In item 24, the control circuit controls an AD conversion
startup trigger interval of AD conversion processing of the
fed-back current and a fetching interval of the rotor rotation
angle value to the arithmetic circuit, to thereby determine the
period in which the feedback information is acquired.
[0104] According to this, the same operational effect as that of
item 10 is exhibited.
[0105] [28] <CPU Detects Load Fluctuation to Change Sampling
Period>
[0106] In items 28 to 33, a function of the follow-up control
portion in items 20 to 27 is replaced by a CPU. In item 19, the
control unit (26A) includes an arithmetic circuit (47) that
performs the predetermined arithmetic processing. The CPU (20)
controls a sampling period of feedback information so as to be
variable, determines whether a predetermined load fluctuation is
generated in the alternating-current motor, shortens a period in
which the feedback information is acquired until control of the
alternating-current motor follows the load fluctuation in case that
the load fluctuation is determined to be generated, and returns the
period in which the feedback information is acquired to a reference
value in case that the control of the alternating-current motor
follows the load fluctuation.
[0107] According to this, the same operational effect as that of
item 11 is exhibited.
[0108] [29] <Load Fluctuation Sensing in CPU (Rotor Angle, Motor
Current)>
[0109] In item 29, the CPU senses the predetermined load
fluctuation from the rotor rotation angle value or the motor
current value.
[0110] According to this, the same operational effect as that of
item 12 is exhibited.
[0111] [30] <Load Fluctuation Sensing in CPU (Road Surface
Reflectance)>
[0112] In item 29, the CPU further predicts the predetermined load
fluctuation from state detection information of a traveling road
surface of a vehicle.
[0113] According to this, the same operational effect as that of
item 13 is exhibited.
[0114] [31] <Filter Arithmetic Operation, Averaging Arithmetic
Operation>
[0115] In item 28, the predetermined arithmetic processing in the
arithmetic circuit includes coordinate conversion processing for
converting the motor current value and the rotor rotation angle
value into a two-phase current value, and filter arithmetic
processing or average arithmetic processing for the two-phase
current value on which coordinate conversion is performed.
[0116] According to this, the same operational effect as that of
item 14 is exhibited.
[0117] [32] <Arithmetic Gain Control in CPU>
[0118] In item 31, the CPU changes a gain of the filter arithmetic
processing or the average arithmetic processing in the arithmetic
circuit, as necessary, in case that the period in which the
feedback information is acquired is set to be short, and performs
control for returning the gain of the filter arithmetic processing
or the average arithmetic processing to the initial value incase
that the period in which the feedback information is acquired is
returned to the reference value.
[0119] According to this, the same operational effect as that of
item 15 is exhibited.
[0120] [33] <Sampling Period Control in CPU; Startup Trigger
Interval of AD Conversion>
[0121] In item 31, the CPU controls an AD conversion startup
trigger interval of AD conversion processing of the fed-back
current and a fetching interval of the rotor rotation angle value
to the arithmetic circuit, to thereby determine the acquisition
period of the feedback information.
[0122] According to this, the same operational effect as that of
item 16 is exhibited.
[0123] [34] <ECU>
[0124] In any of items 10 to 17, the motor control device
constitutes an ECU which is connected to an in-vehicle network.
[0125] According to this, the motor drive device is suitable for an
EV or an HV.
2. Further Detailed Description of the Embodiments
[0126] A further detailed description of the embodiments will be
given. Meanwhile, in all the drawings for the purpose of describing
a mode for carrying out the invention, components having the same
functions are denoted by the same reference numerals and signs, and
thus the description thereof will not be repeated.
[0127] <<Motor Drive Device>>
[0128] FIG. 1 illustrates an example of a motor drive device. A
motor drive device 1 shown in the drawing is a device that drives
an alternating-current motor (MT) 2 which is a motive power source
for EV or HV traveling. Although not particularly limited, a motor
shaft of the alternating-current motor 2 is connected to a wheel 4
through a transmission 3. Further, the motor shaft of the
alternating-current motor 2 has a resolver for detecting its
rotation angle connected thereto. Although particularly not shown
in the drawing, in a case of in-wheel motor drive, an
alternating-current motor and a resolver are provided independently
for each wheel.
[0129] The motor drive device 1 includes a 3-phase voltage-type
inverter 10 using six insulated gate bipolar transistors (IGBT), a
pre-driver 11, a resolver digital converter (RD converter) 12, a
microcomputer (MCU) 13 which is an example of the motor control
device, and a network transceiver (TRC) 14 which is connected to an
in-vehicle network 6 such as CAN, and constitutes one ECU
(Electronic Control Unit).
[0130] A drive current of the inverter 10 is detected as motor
currents Iv and Iw, for example, by a current sensor 14, and is fed
back to the microcomputer 13.
[0131] The resolver 5 inputs an excitation signal Smg from the RD
converter 12, to output sine and cosine resolver signals Srs from a
detection coil in accordance with the angle of a rotor. The RD
converter 12 generates a motor rotation phase signal Rp such as an
encoder-equivalent pulse signal from the resolver signal Srs and
feeds back the generated signal to the microcomputer 13.
[0132] Although not particularly limited, the microcomputer 13 is
formed in one semiconductor substrate such as single crystal
silicon by a CMOS circuit manufacturing technique or the like.
[0133] The microcomputer 13 is an example of the motor control
device that performs feedback control on the motor current which is
output by the inverter on the basis of a drive command. Here, the
pre-driver 11 and the RD converter 12 serve as external components
of the microcomputer 13, but can also be built into the
microcomputer 13.
[0134] The microcomputer 13 is connected to the network transceiver
14 through a network controller (COM) 22, and receives a detection
signal from a sensor (SNSR) 7, or communicates with other ECUs (not
shown).
[0135] The microcomputer 13 includes a CPU (Central Processing
Unit) 20 as a central processing unit that executes a program, and
an internal memory (MRY) 21 which is constituted by a non-volatile
memory that stores a program executed by the CPU 20 or control data
and a RAM which is used in a work area of the CPU 20. The
microcomputer 13 includes a PWM circuit (PWM) 23 that outputs
3-phase PWM pulse signals Pu, Pv, and Pw for driving the inverter
10 to the pre-driver 11. Further, the microcomputer 13 includes an
AD converter (ADC) 24 that converts an analog signal to a digital
signal, a counter (COUNT) 25 that inputs and counts a phase signal,
and an accelerator (ACCL) 26 as an arithmetic circuit that performs
a required arithmetic operation and arithmetic control. Meanwhile,
a circuit block inside the microcomputer 13 is capable of a signal
interface through an internal bus 27 which is representatively
shown.
[0136] The AD converter 24 performs AD conversion on the motor
currents Iv and Iw of the motor in accordance with a sampling
period indicated from the CPU 20 or the accelerator 26 to obtain
motor current values iv and iw, and outputs the resultant to the
accelerator 26 or the like. The counter 25 counts the motor
rotation phase signal Rp which is input through the RD converter 12
to acquire an electrical angle (rotor rotation angle value
indicating a rotor position of the motor) .theta., and the acquired
electrical angle .theta. is used for each required sampling period
by the CPU 20 or the accelerator 26. The motor current values iv
and iw and the electrical angle .theta. are an example serving as
feedback information which is fed back to the accelerator 26 by the
driving of the alternating-current motor.
[0137] FIG. 2 illustrates, in principle, a PWM control function for
vector control of the alternating-current motor in a CPU and an
arithmetic function of the accelerator.
[0138] In a case of a vehicle, an output torque command of the
motor is first determined from an accelerator opening degree, a
vehicle speed or the like. In order to perform the vector control
on the basis of this output torque command, d-axis and q-axis
current command values id and iq are then calculated as drive
command values. The output torque command is given to the CPU 20
through, for example, the network 6, and thus the CPU 20 calculates
the d-axis current command value id and the q-axis current command
value iq.
[0139] The d-axis current command value id and the q-axis current
command value iq which are obtained are supplied to subtracters 30d
and 30q. Here, deviations .DELTA.id and .DELTA.iq between a present
d-axis current value idc and a present q-axis current value iqc are
obtained. Regarding the obtained deviations .DELTA.id and
.DELTA.iq, in PI arithmetic units 32d and 32q, a d-axis voltage
command value Vd and a q-axis voltage command value Vq are
calculated by a PI (Proportional-Integral) control arithmetic
operation based on a proportional integral algorithm. That is, the
d-axis and q-axis currents idc and iqc are corrected by the sum of
a P feedback value obtained by multiplying the deviations .DELTA.id
and .DELTA.iq by a P gain (proportional gain) and an I feedback
value obtained by multiplying an integrated value of the deviations
.DELTA.id and .DELTA.iq by an I gain (integration gain), and these
values are converted into voltage command values to calculate the
d-axis and q-axis voltage commands Vd and Vq.
[0140] The calculated d-axis and q-axis voltage command values Vd
and Vq are supplied to a coordinate conversion portion 34 that
performs coordinate conversion from 2-phase to 3-phase, and are
subject to coordinate conversion from two axes of d and q to three
axes of U, V, and W, and thus 3-phase motor drive voltage commands
Vu, Vv, and Vw of which the phases are different from each other by
120 degrees are obtained. The obtained motor drive voltage command
values Vu, Vv, and Vw are converted into the PWM pulse signals Pu,
Pv, and Pw in the PWM circuit 23. This conversion is performed by
comparing, for example, the motor drive voltage commands Vu, Vv,
and Vw with, for example, a triangular wave of a predetermined
frequency which is a carrier signal of a predetermined frequency
(carrier frequency), and determining the duty ratio of the PWM
pulse signals Pu, Pv, and Pw. In this manner, the PWM pulse signals
Pu, Pv, and Pw of each phase are formed, and these pulse signals
are supplied to the inverter 10 through the pre-driver 11.
[0141] The inverter 10 is configured to receive a direct-current
voltage from a battery (not shown) between a positive-electrode
line and a negative-electrode line, and to convert the received
voltage into a 3-phase alternating current. For example, three
series circuits are configured to be connected to each other
between the positive-electrode line and the negative-electrode
line, each of the series circuits being composed of two
complementary insulated gate bipolar transistors, and a coupling
node between the two complementary insulated gate bipolar
transistors in each series circuit serves as an output of each
phase. Each of the series circuits is operated complementarily
switchably in the PWM pulse signals Pu, Pv, and Pw, and thus a
3-phase motor drive current is generated. The motor drive current
is supplied to the motor 2, and the motor 2 is driven by an output
according to the output torque command.
[0142] Here, the phase of the motor drive current is determined in
accordance with the electrical angle (rotor position) of the motor
2. Therefore, the resolver 5 as an angle sensor is installed in the
motor 2, the resolver signal Srs is output from the resolver 5 to
the RD converter 12, and the RD converter 12 generates the motor
rotation phase signal Rp.
[0143] The motor rotation phase signal Rp is counted in the counter
25 and has an offset error added thereto, and thus the electrical
angle .theta. of the alternating-current motor 2 is calculated. The
electrical angle .theta. is supplied to the coordinate conversion
portion 34 and thus is used in phase control of the motor drive
voltage commands Vu, Vv, and Vw. In addition, the electrical angle
.theta. is supplied to the coordinate conversion portion 40 of the
accelerator 26, and is used in the coordinate conversion of the
motor current values iv and iw from 3-phase to 2-phase.
[0144] The coordinate conversion portion 40 performs coordinate
conversion on the motor current values iv and iw, which are output
from the AD converter 24, to the d and q-axes using the electrical
angle .theta., and calculates a d-axis current value idm and a
q-axis current value iqm. The coordinate conversion arithmetic
portion 34 may acquire the electrical angle .theta. required for a
coordinate conversion arithmetic operation for each carrier period
of the PWM circuit 23. On the other hand, the coordinate conversion
portion 40 needs to acquire the electrical angle .theta. required
for a coordinate conversion arithmetic operation for each sampling
period of the motor current values iv and iw.
[0145] The d-axis current value idm and the q-axis current value
iqm which are calculated are supplied to aggregate arithmetic
portions 41d and 41q, and are subject to a predetermined arithmetic
operation. The arithmetic results are supplied to the
above-mentioned subtracters 30d and 30q as a present d-axis current
value id and a present q-axis current value iq.
[0146] Here, a period in which the motor current values iv and iw
and the electrical angle .theta. are generated is not limited to a
carrier period unit of the PWM circuit 23, and is set to a short
period of one severalth of the carrier period, to take into
consideration the drastic load fluctuation of the
alternating-current motor 2 so as to be capable of following the
motor control. In case that a predetermined load fluctuation occurs
in the alternating-current motor 2, the motor current values iv and
iw and the electrical angle .theta. are acquired at an interval
shorter than the carrier period of the PWM circuit 23, and the
aggregate arithmetic portions 41d and 41q perform predetermined
arithmetic processing, such as filter arithmetic processing or
average arithmetic processing, for aggregating a plurality of
d-axis current values idm and q-axis current values iqm for one
period of the carrier period on which the coordinate conversion
arithmetic operation is sequentially performed in the acquisition
period, in a comparison target for one period of the carrier
period. Meanwhile, in case that the sampling period of the motor
current values iv and iw and the electrical angle .theta. is set to
be equal to the carrier period of the PWM circuit 23, the filter
arithmetic processing or the average arithmetic processing for the
aggregation has no substantial meaning, and sampled information is
output to the post-stage as it is.
[0147] Here, a relationship between the sampling period in which
the motor current values iv and iw and the electrical angle .theta.
are acquired and the carrier period will be described.
[0148] FIG. 3 conceptually illustrates a case where the sampling
period in which the motor current values iv and iw and the
electrical angle .theta. are acquired and the carrier period are
coincident with each other. Here, fcrr is a conceptual carrier
period of the PWM circuit 23, Iu is a 1-phase motor current
waveform, Tsm is a sampling timing of the motor current, and Pu and
Pub are 1-phase complementary PWM pulse signals. In a PWM operation
in this example, the motor current values iv and iw and the
electrical angle .theta. are sampled one time for each carrier
period, and a coordinate conversion arithmetic operation (vector
arithmetic operation) is performed on the resultant. The result is
reflected in the setting of the next pulse duty of the PWM pulse
signal. In this case, in case that a motor rotation quickens
suddenly due to the slip of a wheel or the like, the frequency of a
motor current waveform increases in accordance therewith, and thus
the motor current can be acquired by AD conversion. However, since
the frequency of the motor current waveform is higher than the
carrier period, it is not possible to sample a sufficient number of
times of the motor current value with respect to the waveform of
its sinusoidal wave, and not to follow a PWM waveform in a
direction in which the high rotation of the motor in response to
the sudden fluctuation of the load is suppressed. In short, as
illustrated in FIG. 4, the motor drive current is easily
represented by a sinusoidal wave through a PWM pulse in the motor
current having a low frequency in case that the motor rotation is
slow, but the motor drive current is not easily represented by a
sinusoidal wave through the PWM pulse in the motor current having a
high frequency due to a fast motor rotation. The influence of
one-time switching of a pulse waveform generation switch on which a
switching operation is performed increases in accordance with the
comparison result. In order to reduce the influence, the number of
switching may be increased by increasing the number of times of
sampling. However, in case that the motor rotation becomes too fast
with respect to the carrier period in which the PWM operation is
specified, the earliest motor current is not able to be acquired in
a sinusoidal shape even in a case where the sampling interval of
the motor current is shortened.
[0149] Consequently, since the PWM pulse in which the acquired
current value is reflected is dependent on the carrier period, a
plurality of motor current values or the like acquired as feedback
information during the carrier period have to be arithmetically
calculated collectively by filtering or averaging, to thereby
reflect the resultant in a duty of the PWM pulse. The arithmetic
portions 41d and 41q perform the arithmetic operation.
[0150] FIG. 5 conceptually illustrates a process in case that the
sampling period in which the motor current values iv and iw and the
electrical angle .theta. are acquired is made shorter than the
carrier period, as such a processing method. In the PWM operation,
the motor current values iv and iw and the electrical angle .theta.
are sampled multiple times for each carrier period to perform the
coordinate conversion arithmetic operation (vector arithmetic
operation) on the resultants, and the coordinate conversion
arithmetic results idm and iqm are aggregated in a comparison
target for one period of the carrier period by performing a
predetermined arithmetic operation such as averaging in the
arithmetic portions 41d and 41q. The aggregated arithmetic results
are reflected in the setting of the next pulse duty of the PWM
pulse signal. Thereby, even in case that the motor rotation
quickens suddenly due to the slip of a wheel and thus the frequency
of the motor current waveform increases, a sufficient number of
times of the motor current value is sampled with respect to the
waveform of its sinusoidal wave, and thus it is possible to follow
a PWM waveform in a direction in which the high rotation of the
motor is suppressed.
[0151] Hereinafter, a description will be given of a specific
control mode for following a PWM pulse in a direction in which the
high rotation of the alternating-current motor due to a drastic
load fluctuation is suppressed.
[0152] <<First PWM Pulse Follow-up Control Mode for Load
Fluctuation>>
[0153] A first PWM pulse follow-up control mode will be described.
In FIG. 2, functional blocks of the subtracters 30d and 30q, the PI
arithmetic units 32d and 32q, the coordinate conversion portion 34
and the like except for the accelerator 26 and arithmetic sequence
control using these blocks are assumed to be realized by the CPU 20
and its operating program. The accelerator 26 is realized by
hardware different from the CPU 20.
[0154] In FIG. 2, the acquisition period (that is, startup period
of an AD conversion operation for the motor currents Iv and Iw) of
the motor current values iv and iw in the AD converter 24 is
synchronized with the carrier period of the PWM circuit 23 by the
control of the CPU 20. Similarly to this, the acquisition period of
the electrical angle .theta. in the counter 25 becomes also the
same as the startup period of the AD conversion operation.
Hereinafter, such a period is simply denoted by the sampling period
of feedback information (motor current values iv and iw and
electrical angle .theta.) in the accelerator 26.
[0155] The sampling period of the feedback information is
synchronized with the carrier period of the PWM circuit 23, and the
synchronous control thereof includes synchronous control of the
sampling period in the CPU and independent synchronous control of
the sampling period in the accelerator 26, in the present
embodiment.
[0156] The synchronous control of the sampling period in the CPU 20
is control conforming the sampling period to the carrier period,
that is, control capable of once sampling the feedback information
(motor current values iv and iw) for each carrier period. For
example, the startup timing of a conversion operation of the AD
conversion circuit 24 is set for each carrier period, and the
electrical angle .theta. is output from the counter 25 in a period
based thereon. Here, the carrier period of the PWM circuit 23 is
set, in principle, in accordance with a torque command which is
capable of being grasped from a current command value by the CPU
20. For example, a loss of PWM pulse drive is reduced even in case
that the burden of control increases by decreasing the carrier
period at the time of requiring a large torque, and preferentially,
the burden of controlling the PWM pulse drive is not caused to
increase by increasing the carrier period in case that a small
torque may be satisfactory.
[0157] The independent synchronous control of the sampling period
in the accelerator 26 is control for determining whether the
accelerator 26 generates a predetermined load fluctuation in the
alternating-current motor 2, shortening the sampling period of the
feedback information (motor current values iv and iw and electrical
angle .theta.) initialized by the CPU 20 until the high rotation of
the alternating-current motor 2 subsides (until the PWM waveform is
followed up in a direction in which the high rotation of the motor
is suppressed) in case that the load fluctuation is determined to
be generated, and returning the sampling period of the feedback
information to a reference value which is an initialized value in
case that the motor control follows the load fluctuation.
[0158] FIG. 6 illustrates a configuration of the accelerator 26 for
performing the synchronous control of the sampling period. The
accelerator 26 includes a follow-up control portion 42, a load
fluctuation determination portion 43, correction portions 44 and
45, and registers RG1.theta. to RG12t, in addition to the
coordinate conversion portion 40 and the aggregate arithmetic
portions 41d and 41q. The coordinate conversion portion 40 and the
aggregate arithmetic portions 41d and 41q are an example of an
arithmetic circuit 47 that performs an arithmetic operation for
aggregating the feedback information. The follow-up control portion
42 and the load fluctuation determination portion 43 are an example
of a control circuit 46 that controls the sampling period of the
feedback information so as to be variable in case that a
predetermined load fluctuation is generated in the
alternating-current motor 2.
[0159] The register RG1.theta. is supplied with the electrical
angle .theta. which is acquired in the counter 25, and the register
RG2iviw is supplied with the motor currents iv and iw which are
acquired in the AD converter 24. An offset value is set in the
registers RG3ofs and RG4ofs by a CPU 120. The correction portion 44
corrects the motor currents iv and iw, supplied to the register
RG2iviw, to the offset value which is set in the register RG3ofs.
For example, in case that the AD conversion range of the AD
converter is set to 0 to 5 V, a process of correcting an AD
conversion value obtained thereby to a conversion value centering
on 2.5 V is performed. The correction portion 45 corrects the
electrical angle .theta., supplied to the register RG1.theta., to
the offset value which is set in the register RG2ofs. For example,
correction for offsetting misalignment due to a mechanical error
such as the rotor position of the resolver 5 is performed. The
motor currents iv and iw and the electrical angle .theta. which are
corrected by the correction portions 44 and 45 are converted into
the d-axis current value idm and the q-axis current value iqm by
the coordinate conversion portion 40. The electrical angle .theta.
is supplied to the register RG58, and the electrical angle .theta.
which is supplied to the register RG58 is referenced in
synchronization with a required coordinate conversion timing by the
CPU 20 constituting the coordinate conversion portion 34.
[0160] The setting of a startup trigger of an AD conversion
operation by the AD converter 24 is performed on the register
REG7adt by the CPU 20, or is performed on the register REG7adt by
the follow-up control portion 42. The setting of the register
REG7adt is performed by only the CPU 20 in the synchronous control
of the sampling period in the CPU 20. On the other hand, in the
independent synchronous control of the sampling period in the
accelerator 26, the register REG7adt which is initialized by the
CPU 20 is reset by the follow-up control portion 42, and thus an AD
conversion operation period in the AD converter 24 is controlled so
as to be variable.
[0161] The coordinate conversion portion 40 sequentially performs
coordinate conversion in synchronization with the sampling period
of the motor current in the AD converter 24, and the d-axis current
value idm and the q-axis current value iqm on which the coordinate
conversion is performed are subject to a filter arithmetic
operation or an averaging arithmetic operation in the carrier
period alone, respectively, in the aggregate arithmetic portions
41d and 41q. The averaging arithmetic operation is, for example, a
process of performing an arithmetic average or a weighted average
on the d-axis current value idm and the q-axis current value iqm in
the carrier period alone. The filter arithmetic operation is, for
example, a process of setting the d-axis current value idm and the
q-axis current value iqm passing through a bandpass such as a
bandpass filter, or the average value thereof, to the d-axis
current value id and the q-axis current value iq. Gains which are
set in the registers RG8g and RG9g are designated in arithmetic
processing in the arithmetic portions 41d and 41q. For example, a
weighted value for the average value on which the arithmetic
operation is performed is determined to be a gain in a case of an
arithmetic averaging process, and a weighted value for each of the
d-axis current value idm and the q-axis current value iqm is
determined to be a gain in a case of a weighted averaging process.
In addition, in the filter arithmetic processing, a bandpass value
or a cutoff value is determined to be a gain in accordance with the
magnitudes of the d-axis current value id and the q-axis current
value iq which are immediately preceding filter arithmetic
results.
[0162] The setting of a corresponding gain is performed on the
registers RG8g and RG9g by the CPU 20, or is performed on the
registers RG8g and RG9g by the follow-up control portion 42. In the
synchronous control of the sampling period in the CPU, the setting
of the registers RG8g and RG9g is performed by only the CPU 20. On
the other hand, in the independent synchronous control of the
sampling period in the accelerator 26, RG8g and RG9g which are
initialized by the CPU 20 are reset by the follow-up control
portion 42. By this resetting, it is possible to cope with a
difference in a weight included in one piece of sample data in
response to a change (change in the sampling period of the motor
current) in the AD conversion operation period by the AD converter
24, or a difference in an influence which is given to one pulse of
the PWM pulse by one piece of sampling data.
[0163] The d-axis current value id and the q-axis current value iq
on which the arithmetic operation is performed by the arithmetic
portions 41d and 41q are set in the registers RG10pid and RG11kiq,
the d-axis current value id and the q-axis current value iq which
are set are referenced by the CPU 20, and the process of the
subtracters 30d and 30q is performed.
[0164] Although not particularly limited, the load fluctuation
determination portion 43 detects the fluctuation of a motor load on
the basis of the q-axis current value iqm which is a component
corresponding to a torque of the motor load. For example, the
fluctuation of the motor load is detected on the basis of the
change rate of the q-axis current value iqm. The detection result
thereof is given to the follow-up control portion 42. In addition,
the load fluctuation can also be detected by the CPU 20 acquiring a
detection signal of the sensor (SNSR) 7 of FIG. 1 which is disposed
outside the microcomputer 1 from the network 6. For example, the
sensor 7 receives a reflected signal from a vehicle traveling road,
and the CPU 20 gives the change of the reflected signal as a road
surface state signal RDSI to the follow-up control portion 42. The
follow-up control portion 42 predicts a drastic load drop of the
alternating-current motor on the assumption of sudden entrance into
a freezing road surface or a rainwater road surface on the basis of
the road surface state signal RDST.
[0165] In case that a drastic drop of the motor load, that is, a
drastic torque drop is detected on the basis of the detection
output of the load fluctuation determination portion 43 or the road
surface state signal RDST, the follow-up control portion 42 starts
the autonomous synchronous control of the sampling period in the
accelerator 26. Control data required for this control is set in
the registers RG11t and RG12t, for example, by the CPU 20. For
example, the control data is data indicating the carrier period of
PWM, and data indicating the shortening degree of the sampling
period of the autonomous synchronous control, the change degree of
the gain, and the like. The follow-up control portion 42 refers to
such control data from the registers RG11t and RG12t, and thus
performs the setting of a startup trigger in the register RG7adt,
the setting of gains in the registers RG8g and RG9g, and the
autonomous synchronous control of the sampling period by
controlling the conversion period of the coordinate conversion
portion 40.
[0166] FIG. 7 illustrates a processing procedure of the autonomous
synchronous control of the sampling period together with a
synchronous control procedure of the sampling period in the CPU.
The sampling period of the feedback information and the gain
control of the arithmetic portions 41d and 41q are aggregated in,
for example, steps S1 to S5 of FIG. 7. Step S1 is a process of the
CPU. The CPU 20 determines the carrier period according to a
necessary torque, sets the control data in the registers RG11t and
RG12t, initializes the startup trigger of AD conversion, that is,
the sampling period in the register REG7adt in accordance with the
carrier period, and sets the gains in the registers RG8g and RG9g.
Thereby, the CPU 20 drives and controls the alternating-current
motor 2 in accordance with the current command values id and iq
while feeding back the motor current.
[0167] In case that the alternating-current motor 2 is rotated by
the control of the CPU 20, the load fluctuation determination
portion 43 determines whether a great fluctuation of the motor load
is generated from the q-axis current value iqm which is acquired in
the coordinate conversion portion 40 (S2). For example, the
determination portion determines a drastic drop of the load caused
by the high rotation of the motor 2 due to the slip of a wheel,
that is, whether the q-axis current value iqm becomes equal to or
less than a threshold. In case that the load fluctuation is
determined to be great, the load fluctuation determination circuit
portion 43 sets a load fluctuation flag (not shown). The load
fluctuation flag can also be referenced by the CPU 20. In a state
where the fluctuation of the motor load is not great, the process
of step S1 is performed in accordance with the load in that
case.
[0168] In case that the fluctuation of the motor load is great, the
follow-up control portion 42 takes charge of the PWM control of the
alternating-current motor, and it is determined whether the motor
control follows the fluctuation of the load (S3). This
determination is performed, for example, by the load fluctuation
determination circuit determining whether the q-axis current value
iqm becomes larger than the threshold as described above. In case
that the control of the motor current does not follow the
fluctuation of the load by restoring the high rotation of the motor
due to the drastic fluctuation of the load, the drive current of
the motor 2 is not formed in a sinusoidal shape, and thus the motor
rotation becomes unstable.
[0169] In case that the control of the motor current does not
follow the fluctuation of the load, the follow-up control portion
42 shortens the sampling period in the carrier period in that case
in accordance with the control data of the register RG12t, and thus
the setting of the gains of the arithmetic portions 41d and 41q is
changed (S4). Thereby, since the sampling number of the motor
current in the carrier period tends to increase, the drive current
based on the PWM pulse can be brought close to a sinusoidal shape.
Thereby, whether the rotation of the motor is restored, that is,
the control of the motor current follows the fluctuation of the
load is determined successively in step S3. In case that the
following is not yet performed for each determination, the setting
change may be performed so that follow-up responsiveness is raised
gradually by further shortening the sampling period in step S4. In
case that the following is performed, the follow-up control portion
42 returns the sampling period and the gain to a state before the
operation in step S4, clears the load fluctuation flag, and
entrusts the synchronous control of the sampling period to the
control of the CPU 20.
[0170] In the synchronous control of the sampling period in the CPU
20, as illustrated in FIG. 8, the number of times of sampling of
the feedback information can also be controlled to multiple times
such as four times in one period of the carrier period. The number
of times of sampling may be determined in accordance with the
magnitude of the carrier period, depending on an operating program
of the CPU 20.
[0171] Further, in the autonomous synchronous control of the
sampling period, as illustrated in FIG. 8, in case that a great
load fluctuation is detected in the middle of the carrier period,
the sampling period may be shorten halfway.
[0172] FIG. 9 illustrates a control mode in the skidding of a wheel
and the return thereof to a normal rotation. At the time of normal
traveling in which the skidding is not generated, a torque
corresponds to the rotational speed of the motor. On the other
hand, in case that a torque is reduced at the time of the skidding
of a wheel due to road surface freezing, the sudden stepping of an
accelerator, or the like, the rotational speed of the motor becomes
faster. In case that a torque increases at the time of the
settlement of the skidding, the rotational speed of the motor
becomes lower. Basic control in the CPU 20 at the time of the
skidding and the settlement of the skidding is as follows. In case
that a wheel skids due to a slip or the like, the rotation of the
motor 20 proceeds, and the load of the motor 20 is reduced. In this
case, the CPU 20 delays a rise in PWM pulse, adjusts a torque of
the motor 20 by performing a process of reducing a duty ratio of
the PWM pulse signal, and attempts to restore the rotation speed of
the motor 20. In that case, the follow-up control portion 42
performs control for generating motor current values id and iq
based on feedback so as to improve follow-up responsiveness of the
motor control with respect to the fluctuation of the load by
shortening the sampling period in response to the sudden
fluctuation of the load such as a reduction in the motor load.
Thereafter, in case that the slip is stopped and the skidding of a
wheel is settled, the rotation of the motor 20 becomes slower, and
the load of the motor 20 increases. Then, the CPU 20 quickens a
rise timing of the PWM pulse, adjusts a torque of the motor 20 by
performing a process of increasing the duty ratio of the PWM pulse
signal, and attempts to restore the rotation speed of the motor 20.
In that case, the follow-up control portion 42 does not respond to
a sudden fluctuation of the load such as an increase in the motor
load, and entrusts control to the CPU 20.
[0173] According to the autonomous synchronous control of the
sampling period in the accelerator 26, the following operational
effects are obtained.
[0174] (1) The sampling period of the feedback current for a great
fluctuation of the motor load is shortened by the accelerator 26
which is separate hardware from the CPU 20, and an arithmetic
operation is performed in which motor current values obtained
thereby are arranged by filtering, averaging or the like, to
thereby perform a process of reflecting the resultant in a duty of
the PWM pulse. Thereby, even in case that the motor rotation
quickens suddenly due to the slip of a wheel and thus the frequency
of the motor current waveform increases, a sufficient number of
times of the motor current value is sampled with respect to the
waveform of its sinusoidal wave, and thus it is possible to follow
a PWM waveform so as to suppress undesired high rotation of the
motor. It is possible to considerably reduce a burden of the CPU 20
in this follow-up control.
[0175] (2) Since it is possible to burden the follow-up control
portion 42 with control of the acquisition period of the feedback
information until the alternating-current motor skids due to a slip
or the like and then recovers, it is possible to reduce a burden of
the CPU 20 in this point.
[0176] (3) Since the follow-up control portion 42 senses the
predetermined load fluctuation from the motor current value iqm, it
is possible to easily acquire the fluctuation of the motor load
without imposing a burden on the CPU 20.
[0177] (4) In case that the sampling period of the feedback
information is shortened, the follow-up control portion 42 changes
the gains of the arithmetic portions 41d and 41q as necessary, and
performs control for restoring the gains of the arithmetic portions
41d and 41q in case that the sampling period is returned to a
reference value. Therefore, it is possible to decrease the gains in
accordance with an increase in the number of acquisitions of the
feedback information so that a response does not become sensitive
without imposing a burden on the CPU 20, or to keep the gains
unchanged due to a fast response in case that the number of
acquisitions of the feedback information increases.
[0178] (5) Since the accelerator 26 is dedicated hardware which is
separate hardware from the CPU 20, the accelerator has a tendency
to optimize the number of arithmetic bits, the arrangement of
registers with respect to the arithmetic circuit, or the like, and
thus is suitable for the speed-up of data processing. The CPU 20
can also perform higher-speed processing at a lower operating
frequency and with a small circuit scale, lower power consumption
can be achieved than in a case where the CPU is entirely burdened,
and it is also contribute to an improvement in the exothermic
characteristics of a product.
[0179] (6) Since the feedback information which is fed back to the
accelerator is the motor current values iv and iw which are
obtained by performing AD conversion on a current which is fed back
from the alternating-current motor 2 and an electrical angle which
is obtained from the rotor position of the alternating-current
motor 2, the feedback information is suitable for vector control of
the alternating-current motor 2.
[0180] (7) Separately from the follow-up control of the follow-up
control portion 42, the CPU 20 requires setting control of the
carrier period of the PWM circuit 23 in accordance with a
relationship with a rotation torque required for the feedback
control, and thus it is economical, in view of a system, for the
CPU 20 to initialize a period in which the feedback information is
acquired in the relationship with the rotation torque.
[0181] (8) Separately from the follow-up control of the follow-up
control portion 42, the CPU 20 also requires gain setting in
response to the setting of the carrier period of the PWM circuit 23
in accordance with the relationship with the rotation torque
required for the feedback control, and thus it is economical, in
view of a system, for the CPU 20 to initialize the gains of the
arithmetic portions 41d and 41q in the relationship with the
rotation torque.
[0182] (9) The follow-up control portion 42 predicts the
predetermined load fluctuation from the state detection information
RDST of a traveling surface that receives a rotational force of the
alternating-current motor, and thus motor rotation control for
suppressing a sudden fluctuation of the motor load can be performed
by faster reaction.
[0183] (10) The follow-up control portion 42 controls an AD
conversion startup trigger interval of AD conversion processing of
a current to be fed back and a fetching interval of the rotor
rotation angle value to the arithmetic circuit, to thereby
determine a period in which the feedback information is acquired,
and thus it is possible to easily control the sampling period of
the feedback information for obtaining the feedback information
without imposing a burden on the CPU 20 in the follow-up
control.
[0184] <<Second PWM Pulse Follow-up Control Mode for Load
Fluctuation>>
[0185] In the first PWM pulse follow-up control mode, a description
has been given on the assumption that the follow-up control portion
42 does not perform a change in the carrier period determined by
the CPU 20. In a second PWM pulse follow-up control mode, the
carrier period as well as the sampling period can be changed with
respect to a sudden fluctuation of the load.
[0186] FIG. 10 illustrates an operation example in case that the
carrier period is changed together with the sampling period with
respect to a sudden fluctuation of the load. In case that there is
a sudden fluctuation of the load, only the number of times of
sampling of the feedback information is increased first in the
process of step S4 of FIG. 7, without changing the carrier period.
Thereby, in case that it is determined that the motor control does
not follow the load fluctuation (S3), follow-up responsiveness may
have a tendency to be improved by lengthening the carrier period
and increasing the number of times of sampling in the next step
S4.
[0187] <<Third PWM Pulse Follow-up Control Mode for Load
Fluctuation>>
[0188] In the first PWM pulse follow-up control mode, a description
has been given on the assumption that the sampling period of the
feedback information is shortened only in case that there is a
sudden fluctuation of the load. In a third PWM pulse follow-up
control mode, the number of times of sampling within the carrier
period is made variable in accordance with the motor load (motor
rotation speed) in the synchronous control of the sampling period
in the CPU 20.
[0189] In the synchronous control of the sampling period in the CPU
20, as illustrated in FIG. 11, the feedback information is sampled
at the rate of one time per period of the carrier period from the
low speed of the motor rotation to the medium speed thereof, and
the feedback information is sampled at the rate of four times per
period of the carrier period at the high speed of the motor
rotation. The number of times of sampling may be determined in
accordance with the motor rotation, depending on the operating
program of the CPU 20. In case that there is a drastic load
fluctuation in a state of the high rotation, the responsiveness of
the PWM control for restoring the motor rotation by further
shortening the sampling period is improved by the synchronous
control of the sampling period in the accelerator 26.
[0190] <<Fourth PWM Pulse Follow-up Control Mode for Load
Fluctuation>>
[0191] In the first PWM pulse follow-up control mode, the follow-up
control portion 42 is adopted giving top priority to a reduction in
the control burden of the CPU 20, and the operations of the
coordinate conversion portion 40 and the arithmetic portions 41d
and 41q which are dedicated arithmetic circuits are controlled. In
a fourth PWM pulse follow-up control mode, on the assumption that
there is a margin capable of burdening the CPU 20A with only the
control thereof, the CPU 20A is caused to execute the control.
[0192] In this case, as illustrated in FIG. 12, in an arithmetic
circuit 26A, the CPU 20A is burdened with a control function of the
follow-up control portion 42 and a determination function of the
load fluctuation determination portion 43. The CPU 20A is
configured to be capable of referring to the motor current value
iqm through the register RG13iqm. The coordinate conversion portion
40 performs coordinate conversion at a necessary timing by the
carrier period and the sampling period in that case being
transferred by control data which is set in the register RG14sync,
from the CPU 20A. Naturally, the CPU 20A performs a setting
operation of a startup trigger for the register RG7adt for
shortening the sampling period at time of the load fluctuation and
a setting operation of gains for the registers RG8g and RG9g
corresponding thereto.
[0193] Meanwhile, other configurations in the fourth PWM pulse
follow-up control mode are the same as those of the first PWM pulse
follow-up control mode, and thus the detailed description thereof
will not be given. The second and third PWM pulse follow-up control
modes can also be applied to the fourth PWM pulse follow-up control
mode.
[0194] According to the fourth PWM pulse follow-up control mode, as
represented by FIG. 6, a burden of the CPU 20A increases in the
control of the acquisition period of the feedback information as
compared to a case where the follow-up control portion 42 is
adopted, but it is possible to cope with the burden flexibly
through software of the CPU 20A.
[0195] As described above, while the invention devised by the
inventor has been described specifically based on the embodiments
thereof, the invention is not limited to the embodiments, and it
goes without saying that various changes and modifications may be
made without departing from the scope of the invention.
[0196] For example, the arithmetic unit in which the accelerator
has been described as an example can also be configured to use all
or some of arithmetic functions of a general-purpose DSP or the
like. An aggregate arithmetic processing function in the arithmetic
unit is not limited to filtering or averaging, and can be
appropriately changed. The state detection information of the
traveling surface is not limited to a change in the reflectance of
a road surface, and a shake or the like responding to the
irregularities of a road surface may be detected. The motor control
device is not limited to a one-chip microcomputer, and may be a
mulita-chip semiconductor module or the like. The rotation angle
detection of the motor shaft is not limited to use of the
resolver.
INDUSTRIAL APPLICABILITY
[0197] The invention can be widely applied to not only an
automobile such as an EV or an HV, but also a motor-driven train
and other machinery and appliances using a motor as a drive
source.
EXPLANATION OF REFERENCE NUMERALS
[0198] 1: motor drive device [0199] 2: alternating-current motor
(MT) [0200] 3: transmission [0201] 4: wheel [0202] 5: resolver
[0203] 6: in-vehicle network [0204] 7: sensor (SNSR) [0205] 10:
inverter [0206] 11: pre-driver [0207] 12: resolver digital
converter [0208] 13: microcomputer (MCU) [0209] 14: current sensor
[0210] Iv, Iw: motor current [0211] Smg: excitation signal [0212]
Srs: resolver signal [0213] Rp: motor rotation phase signal of
layer U, V, and W [0214] 20, 20A: CPU [0215] 21: internal memory
(MRY) [0216] 22: network controller (COM) [0217] 23: PWM circuit
(PWM) [0218] 24: AD converter (ADC) [0219] 25: counter (COUNT)
[0220] 26, 26A: accelerator (ACCL) [0221] 27: internal bus [0222]
iv, iw: motor current value [0223] .theta.: electrical angle (rotor
rotation angle value indicating rotor position of motor) [0224] id:
d-axis current command value [0225] iq: q-axis current command
value [0226] 30d, 30q: subtracter [0227] idc: present d-axis
current value [0228] iqc: present q-axis current value [0229]
.DELTA.id, .DELTA.iq: deviation [0230] 32d, 32q: PI arithmetic unit
[0231] Vd: d-axis voltage command [0232] Vq: q-axis voltage command
[0233] 34: coordinate conversion portion [0234] Vu, Vv, Vw: 3-phase
motor drive voltage command [0235] Pu, Pv, Pw: PWM pulse signal
[0236] 40: coordinate conversion portion [0237] idm: d-axis current
value [0238] iqm: q-axis current value [0239] 41d, 41q: aggregate
arithmetic portion [0240] 46: control circuit [0241] 47: arithmetic
circuit
* * * * *